Vision testing with rendered digital imagery modification under viewer control

ABSTRACT

Tools and techniques for vision testing alter refractive characteristics of rendered digital imagery and use feedback from a test subject to calculate information about errors in the subject&#39;s vision. Some embodiments produce a rendered digital image with vision-realistic rendering, present the test subject with the rendered digital image, accept input from the test subject and change the refractive sharpness of the rendered digital image in response to the input. Then they calculate refractive errors or other information about the test subject&#39;s vision based at least on: input from the test subject leading to a refractive sharpness change made during the changing step, and a refraction model which relates visual acuity to changes in the refractive sharpness of rendered digital imagery.

RELATED APPLICATION

The present application claims priority to, and incorporates byreference, U.S. provisional patent application Ser. No. 60/824,560 filedSep. 5, 2006.

BACKGROUND

A conventional refractor is an optical tool used by optometrists to helpmeasure refractive errors in a person's vision. The person looks throughthe refractor at an image, as their optometrist selects lenses to placein the person's line of sight. The lenses may be made of glass oroptical grade plastic. The refractor holds the lenses in a housing, andit helps organize the lenses in a way that lets the optometrist knowwhich lense(s) the person is looking through to see the image, and whatthe refractive characteristics are of the chosen lenses. The personlooks through the chosen lenses, and tells the optometrist whether agiven choice of lenses in a sequence of lens choices makes the imageappear more focused or less focused—the optometrist may repeatedly askif the view through chosen lenses is “better or worse?” Thus, visiontesting with a refractor is subjective, and proceeds in discretelens-combining steps under the direct supervision of the optometrist.Refractors of this general type have been used for decades. For example,the U.S. trademark PHOROPTOR for eye-testing instruments for testing therefractive media and motor muscles of the eye was registered in 1922(PHOROPTOR is a mark of Leica Microsystems Inc.).

More recently, autorefractors have been created. An autorefractor alsoincludes lenses organized in a housing, but the choice of lenses toplace in the person's line of sight is at least partially made by acomputer program within the autorefractor. The person takes a seat andplaces their chin on a rest. One eye at a time, the person looks at apicture inside the autorefractor. The picture moves in and out of focusas the autorefractor places different lenses in the person's line ofsight, while the autorefractor checks to see whether the correspondingimage is in focus on the person's retina. Several readings can beautomatically taken and averaged. No feedback is needed from the person;the testing is objective. However, it still proceeds in discrete lenscombination steps with a relatively small number of lenses. With anautorefractor, an approximate measurement of a person's refractive errorcan be made quickly and automatically. However, it is not always asaccurate as more labor-intensive and time-consuming tests, so anautorefractor measurement may be used merely as the starting point forthe optometrist to perform a subjective refraction test using lenses ina manually controlled refractor as described above.

In short, a conventional refractor used for vision testing, such as aconventional autorefractor or a PHOROPTOR refractor, operates bychanging the refraction in a beam of a sharp-edged source image untilthe image is perceived by the patient to be in focus, and then notingwhat change in refraction had to be added by the lenses to the patient'sown optical refraction to obtain perceived focus. That added refractionchange—the best-working lens combination—can then be replicated or atleast approximated by eyeglasses or contact lenses, or by refractivesurgery such as LASIK surgery.

It should be noted that the foregoing background was written inhindsight, with the present invention in mind. Thus, the particularcluster of ideas discussed in this background, or their characterizationhere, would not necessarily have been obvious to someone who did nothave the benefit of familiarity with the invention.

SUMMARY

Some embodiments provide a vision testing system which presents a personwith one or more rendered digital images. The vision testing systemaccepts input from the person, in response to which the system changesthe refractive sharpness of the rendered digital image. The systemcalculates information about the person's vision based at least on:input from the person leading to a refractive sharpness change madeduring the changing step, and a refraction model which relates visualacuity to changes in the refractive sharpness of rendered digitalimagery. Some embodiments use vision-realistic rendering based onaberration data to produce the rendered digital image.

More generally, some embodiments operate by changing the sharpness of asource image in a manner that uses digital processing to simulaterefraction changes, without placing physical lenses between the sourceand the viewer to change the refraction in the image received by theviewer. The embodiment then analyzes the sequence of digital imageryrefraction change requests (which indicate the viewer's subjectivechanges in sharpness and/or blurriness) to determine what effect wouldresult from refraction changes made using corrective lenses.

Although many of the examples given herein are systems, the inventionalso provides other embodiments, such as methods and configuredcomputer-readable storage media, for instance. The examples given aremerely illustrative. This Summary is not intended to identify keyfeatures or essential features of the claimed subject matter, nor is itintended to be used to limit the scope of the claimed subject matter.Rather, this Summary is provided to introduce—in a simplified form—someconcepts that are further described below in the Detailed Description.The present invention is defined by the claims, and to the extent thisSummary conflicts with the claims, the claims should prevail. Otheraspects of the present invention will become more fully apparent throughthe following description.

DESCRIPTION OF THE DRAWINGS

A more particular description of the invention will be given withreference to the attached drawings. These drawings only illustrateselected aspects of the invention and thus do not fully determine theinvention's scope.

FIG. 1 is a flow chart illustrating steps of some method, configuredstorage medium, and other embodiments of the present invention;

FIG. 2 is a block diagram illustrating some system and other embodimentsof the present invention;

FIG. 3 shows an example displayed pattern, which is presented on adisplay to a viewer as a starting point in a vision test;

FIG. 4 shows a subsequent displayed pattern which could be produced bythe viewer from the example pattern shown in FIG. 3;

FIG. 5 shows the displayed pattern of FIG. 4 as it is perceived by theviewer;

FIG. 6 shows another example displayed pattern, which is presented on adisplay to a viewer as a starting point in a vision test;

FIG. 7 shows a subsequent displayed pattern which could be produced bythe viewer from the example pattern shown in FIG. 6; and

FIG. 8 shows the displayed pattern of FIG. 7 as it is perceived by theviewer in question.

DETAILED DESCRIPTION Definitions

Reference will now be made to exemplary embodiments such as thoseillustrated in the drawings, and specific language will be used hereinto describe the same. But alterations and further modifications of theinventive features illustrated herein, and additional applications ofthe principles of the invention as illustrated herein, which would occurto one skilled in the relevant art(s) and having possession of thisdisclosure, should be considered within the scope of the invention.

In describing the invention, the meaning of terms is clarified, so theclaims should be read with careful attention to these clarifications.Specific examples are given to illustrate aspects of the invention, butthose of skill in the relevant art(s) will understand that otherexamples may also fall within the meaning of the terms used, and withinthe scope of one or more claims. Terms do not necessarily have the samemeaning here that they have in general usage, in the usage of aparticular industry, or in a particular dictionary or set ofdictionaries. Reference numerals may be used with various phrasings, tohelp show the breadth of a term. The inventor asserts and exercises hisright to provide his own lexicography. Terms may be defined, eitherexplicitly or implicitly, here, elsewhere in the Detailed Description,and/or elsewhere in the application file.

Bearing this in mind, “vision-realistic rendering” is a computer scienceterm of art, and hence is not open to arbitrary or overly generalinterpretation.

A “rendered digital image” is an image produced on a screen, monitor, orother display as the result of a rendering process. The renderingprocess is based on underlying pixel (or equivalently vector) data. Theterm “digital image” is used in contrast with images that are notsusceptible to computational manipulations to achieve blurring or othereffects discussed herein. A conventional eye chart printed on cardboard,for example, is not a digital image, although a digitization processcould be used to create a digital image of such a chart.

A “device” could be made of hardware, software, or both.

The “refractive sharpness” of an image, or of a portion of an image, isthe extent to which the potentially sharp image or image portion hasbeen computationally blurred before being displayed. Such blurring maybe done, for example, using a blur filter. “Blur filter” is a computerscience term of art.

A “refractor interface” is an interface which provides control oversimulated and/or actual lenses to interposition them, through physicalmovement and/or simulation, in between a source image and a viewer, thusaltering the viewer's perceived image. Conventional autorefractors andPHOROPTOR refractors have refractor interfaces. A “software refractorinterface” uses software in an embodiment to simulate a conventionalrefractor interface, which may make it easier for people familiar withconventional refractors to effectively operate embodiments that usefewer or no physical lenses.

Interrelation of Methods, Configured Media, and Systems

FIG. 1 illustrates some method embodiments. However, not every step inthe illustrated flowchart 100 need be included in a given embodimentexactly as shown. In a given embodiment, for example, zero or moreillustrated steps may be repeated, perhaps with different parameters ordata to operate on. Steps in an embodiment may also be done in adifferent order, omitted, combined, or otherwise depart from theillustrated flow, provided that the method performed is operable andconforms with at least one claim.

With reference to FIGS. 1 and 2, a computing system 200 embodimentincludes hardware 206 and software 208. Processors 202 and memories 204are examples of hardware 206. Other hardware 206 may include, forinstance, user I/O devices typically found on digital devices (e.g.,computers, PDAs, cell phones) such as keyboards, screens, touch screens,microphones, speakers, a mouse, a light pen, and so on; such devices maybe part of a user interface 240. Other hardware 206 may also includedisks (magnetic, optical, or otherwise), RAM, EEPROMS or other ROMs,and/or other configured storage media 252. Disks, CDs, flash modules,and the like are forms of memory 204. A memory 204 is a general-purposestorage medium; it may be removable or not, and it may be volatile ornot. A memory 204 is configured with data and instructions 208 tothereby form a configured medium 252 which is capable of causing asystem 200 that has a processor 202 to perform method steps disclosedherein. Accordingly, FIG. 1 helps illustrate configured storage mediaembodiments and system embodiments that perform the methods, as well asillustrating method embodiments.

A given system 200 may include a computer, a collection of communicatingcomputers, another computing device such as a PDA or cell phone, and/ora combination of devices which have one or more processors 202 andcooperating memories 204. Not every item shown in FIG. 2 need be presentin every system embodiment. Although the invention is illustrated intext and drawings by specific examples, other embodiments of theinvention may depart from these examples. For instance, specificfeatures of an example may be omitted, renamed, grouped differently,repeated, instantiated in hardware and/or software differently, or be amix of features appearing in two or more of the examples.

EXAMPLES

One embodiment includes a computing device 200 having a display 266 in auser interface 240, a processor 202 operably connected with a memory204, and software 208 configuring the memory and controlling theprocessor. This embodiment, and some others (e.g., some embodimentshaving multiple processors 202), operate by changing the sharpness of asource image in a manner that simulates refraction changes withoutactually placing physical lenses in the line of sight to change therefraction in the image before it reaches a viewer 256. Theseembodiments effectively propagate subjective changes in sharpness(and/or blurriness) by noting corresponding changes over time in theunderlying source image data 212 to determine 110 what effect to viewervision would result from changes in refraction. That is, whereas aconventional approach holds a source image constant and changesrefraction by interposing lenses between the source image and theviewer, these embodiments change the source image itself in manner thatsimulates refraction changes caused by lenses.

A user interface 240 is implemented in some embodiments as software 208running on conventional hardware, and in other embodiments as acombination of those two components with special purpose hardware thatis used to replicate 128 more closely a conventional vision testingtool's interface. The illustrated interface 240 includes a visualdisplay device 266 (computer screen, or a screen receiving projecteddigital rendered imagery, etc.) with supporting software 244 to present104 rendered digital imagery for viewing. The illustrated interface 240also includes user input hardware 206 (a keyboard, touch screen, mouse,light pen, microphone, etc. with supporting software) and software 248,250 for accepting 106 blurring input and menu selections, etc., software250 for configuring system data 208 such as stored patient data, networkconnectivity, natural language for use in instructions 120, software 242for providing 120 operational instructions, and software 246 forreporting test results and/or reporting recommendations that are madebased on calculations by an acuity calculator 236 and a recommendationmaker 238.

During a rendering step 102, some embodiments render a digital image,that is, they apply a rendering process to source pixels 212 to producescreen pixels 214 which are shown to the viewer 256 on the display 266.Some systems 200 use vision-realistic rendering 102 based on a sequenceof hypothetical patient data 232.

In some conventional vision-realistic rendering systems, actual patientdata is gathered, e.g., by using a Shack-Hartmann device to gatheraberration data from light emerging from a person's eye. See, e.g.,Brian A. Barsky et al. “RAYS (Render As You See): Vision-RealisticRendering Using Hartmann-Shack Wavefront Aberrations”, www dot eecs dotBerkeley dot edu/˜ddgarcia/optical/vrender/papers/psf.pdf, date unknown(per USPTO regulations this domain name is provided in a form notreadily susceptible to confusion with a working hyperlink); WoojinMatthew Yu, “Simulation of Vision Through an Actual Human OpticalSystem”, M. S. Thesis, U. C. Berkeley, 2001; Brian A. Barsky,“Vision-Realistic Rendering: Simulation of the Scanned Foveal Image fromWavefront Data of Human Subjects”, ACM Proceedings of 1^(st) Symposiumon Applied perception in graphics and visualization, pp. 73-81, 2004.Actual patient aberration data could also be gathered using technologydescribed in U.S. Pat. No. 6,761,454 to Lai, et al. The gatheredaberration data are used to render an image which appears to anormally-sighted person as if they were viewing it through the vision ofthe person whose aberration data was used as a basis for the rendering.Vision-realistic rendering could be used, for instance, to generateimages using the optics of various ophthalmic conditions such ascataracts, glaucoma, keratoconus, macular degeneration, and diplopia, tohelp educate doctors and patients about the effects of these visualdefects.

By contrast, in some embodiments of the present invention an actualpatient aberration data set need not be used. Instead, a sequence ofhypothetical aberration data sets 232 is used, such that thehypothetical data sets plus the patient's aberration converge toward(and preferably result in) a specified perceived target image 268.Vision-realistic rendering 102 as used in these embodiments helpsfunctionally define a rigorous mapping 220-228 between measurements ofpatient 256 vision aberration and displayed images 214. The embodimentsprovide (among other things) a rigorous mapping between displayed images214 and perceived images. By utilizing vision-realistic rendering inreverse 124 in accordance with an embodiment, one can obtain data whichrigorously lead to measurements of patent vision aberration.Vision-realistic rendering is used 124 “in reverse” in the sense thatinstead of starting with measurements of a human subject's visionaberrations, one ends up with such measurements 232.

Shack-Hartmann data 232 are only one way to help model or mathematicallydescribe the refractive properties of the optical system of a person256. Other models that can be used by a rendering subsystem 218 tocontrol generation 102 of display images 214 can also be used inembodiments, when the model used provides some clinically useful measureof myopia, hyperopia, astigmatism, and/or other visual aberrations in aviewed image 268, in (or translatable to) diopters or another suitableunit.

In some embodiments, the model 220-228 is used by the renderingsubsystem 218 to generate an initial display image 214, and the patient256 is verbally given 120 a target image into which the patient converts106, 108, 104 the display image, at least from the patient's perspective268. The transformation of the initial display image 212/214 into afinal display image 212/214 respectively, is measurable, and has meaningin terms of diopters or other aberration units. Because the finaldisplay image is perceived 268 as the specified 120 target image, butdiffers in the source space 212/214 from that target image, the extentto which the final display image differs from the target image is ameasurement of the patient's visual aberration(s). That is, to theextent that the defect in viewer perception is a linear operator or else(like much refraction) can be adequately approximated 110 as beinglinear, the difference between the initial display image and the targetimage can be calculated 110 as the sum of the difference between theinitial display image and the final display image, and the patient'saberration. Stated differently, an acuity calculator 236, 208 maycalculate a target image by treating the initial displayed image asbeing modified by two filters, with one filter defined over time bypatient manipulation 106 of the displayed images 214 through the userinterface 240, and the other filter being provided by the patient's owneye(s):

-   -   (1)        Display_(initial)+(Display_(Final)−Display_(initial))+PatientAberration=TargetImage        or more simply:    -   (2) Display_(Final)+PatientAberration=TargetImage, so    -   (3) PatientAberration=TargetImage−Display_(Final)        That is, to the extent that the target image and the final        displayed image (which the patient perceives as close to or        identical with the target image) can be described in meaningful        optometric terms, their calculated 110 difference is a measure        208 of the patient's refractive error or other visual        aberration.

Accordingly, mathematical models 220-228 of sight which are correlatedwith optometric measures, or which can be thus correlated analyticallyand/or empirically, and which are also useful in guiding computergraphic rendering engines 230, can be suitable for use in embodimentsaccording to the present invention. Some vision-realistic rendering 218uses Object Space Point Spread Functions in a mathematical model 220 ofsight; see, e.g., the RAYS reference above. Other mathematical models ofsight used in some embodiments 218 include an asymmetric ellipsoid model222 described in Daniel D. Garcia et al, “CWhatUC: A Visual AcuitySimulator”, Proceedings of SPIE, Volume 3246, Ophthalmic TechnologiesVIII, Pascal O. Rol, Karen M. Joos, Fabrice Manns, Editors, June 1998,pp. 290-298; a spline-based model 224 described in U.S. Pat. No.6,241,355 to Barsky; a generalized imaging system model 228 described inPatrick Y. Maeda, et al., “Integrating Lens Design with Digital CameraSimulation”, Proceedings of SPIE-IS&T Electronic Imaging, SPIE Vol.5678, 2005; models 228 of blurring and other visual characteristicsdescribed in Brian A. Barsky, et al. “Camera Models and Optical SystemsUsed in Computer Graphics” (Part I and Part II), Proceedings of the 2003International Conference on Computational Science and its Applications(ICCSA'03), Montreal, May 18-21, 2003, Second International Workshop onComputer Graphics and Geometric Modeling (CGGM'2003), Springer-VerlagLecture Notes in Computer Science (LNCS), Berlin/Heidelberg, pages246-265; and a model 226 of blurring described in Jaroslav Kautsky, etal., “A new wavelet-based measure of image focus”, Pattern RecognitionLetters 23 (2002) 1785-1794. The present invention is not, however,limited to any particular mathematical model of the human eye or anyparticular mathematical model of optical system characteristics.

One system 200 works as follows. A computer-generated scene is rendered102, based on and/or otherwise corresponding to a hypothetical set ofpatient aberration measurements 232, e.g., a hypothetical Shack-Hartmannaberration data set for an eye having 20/20 vision. The scene 214 mayshow objects at different depths, may show three-dimensional objects,may have a specified (small to large) depth of field, and otherwise mayhave characteristics of interest in vision-realistic rendering.

The rendered scene 214 is displayed 104 to a user 256, and the user isinstructed 120 to use a light pen 206 or other interface 240 tool tomake all parts of the scene 214 equally blurry. In a variation, theviewer is instructed 256 to make two or more specified portions of ascene, or two scenes, equally blurry. As the user moves 106 the lightpen over a given part of the scene, that part of the scene is blurred108 with a blur filter 216 and re-rendered 102 and displayed 104, usingvision-realistic rendering techniques and tools 230. The blur filter 216correlates 110 sharpness changes 108 with optometric measures. That is,in coordination with the blurring 108, the hypothetical aberration dataset 232 is updated. Those aberration data set readings could produce thecorresponding blur in a conventional forward-operating vision-realisticrendering system. When the user is done blurring the image and causingcorresponding aberration data set updates, this display-blur-update loop126 is exited. The user 256 may be asked to expressly indicate when theuser is done, e.g., by pressing a user interface 240 button or selectingan icon 240, or the system 200 may presume that the user is done if nofurther user input is received after some predetermined timeout period,e.g., ten seconds. Point spread functions 220 may be used in aberrationdata sets 232—as proxies for Shack-Hartmann data sets 232—in someembodiments.

Display-blur-update loops may also be provided 126 without using 124reverse vision-realistic rendering, in embodiments which use refractionmodels 228 not reliant on a vision-realistic rendering engine 230.Recall that “vision-realistic rendering” is a computer science term ofart. The term “display-blur-update loop”, which was coined for useherein, encompasses loops in which blurring is done by vision-realisticrendering techniques as well as loops in which blurring is done by otherrendering techniques.

The aberration data set 232 thus produced should correspond partly orfully to an actual aberration data set obtained contemporaneously by aShack-Hartmann device for the same user eye(s). But the embodimentproduces the aberration data set as just described, through aninteractive reverse vision-realistic rendering loop 124, instead ofobtaining the aberration data set by use of a Shack-Hartmann device.However, it may be helpful for clinical tests and/or for calibration tosometimes produce aberration data sets for one or more subjects 256 inboth ways—by interactive reverse vision-realistic rendering 124, and byactual Shack-Hartmann device measurements—and to then compare 236 thosedata sets. The mapping between corrective prescriptions andShack-Hartmann aberration data sets can then be used by software 238 toproduce 112 a corrective prescription for the user 256 from theaberration data set 232 that was obtained 122 by interactive reversevision-realistic rendering.

The phenomenon of viewer accommodation to blurriness is known. See,e.g., Michael A. Webster et al., “Neural adjustments to image blur”,Nature Neuroscience, volume 5 no. 9, pp. 839-840, September 2002. Someembodiments include software 234 to measure 116 and compensate 108 foraccommodation effects. In one system 200, the user 256 is presented 104a first displayed image 214, and guided through blurring 106, 108 of atleast portions of that image to obtain an aberration data set 232 asdescribed above. Then a second displayed image 214 is displayed 104.This second image is blurred 216 a measured quantum more than the firstdisplayed image. The blurring quantum may be determined by software 234using vision-realistic techniques per Barsky, for instance, or cameraautofocusation measures per Kautsky. The user 256 is guided throughblurring of at least a portion of the second image to obtain a secondaberration data set 232. A third, further blurred image is displayed,and a third aberration data set is obtained 232. A calculated 116 trendin blurring should then match the trend in aberration 232. It may alsobe determined experimentally whether these trends are linear or conformwith some other specified mathematical relationship, which can then beused to estimate 116 viewer accommodation. Regardless, they provide datawhich show the progress of a viewer's accommodation over time, and whichcan be read in reverse time and in correlation with the aberration datasets to obtain 116 an aberration data set 232 matching a point havingzero (or acceptably small) accommodation.

In this example, three blur values and corresponding aberration sets areused in estimating 116 accommodation, but in other embodiments fewer ormore blur values, and fewer or more display images, for example, can beused. The blurriness of display images 214 could also be held constantby the accommodation estimation module 234, for instance, instead ofbeing increased. Blurriness could also be decreased by sharpening imagesto be displayed. Indeed, negative changes to blurriness (that is, havingthe rendering subsystem 218 increase sharpness per Webster et al. orotherwise) could be done in any of the embodiments discussed above, inplace of or in addition to, positive changes to blurriness, that is,changes that increase blurriness.

Some embodiments control 114 testing conditions to influence factors ofthe type known now or subsequently developed, in optometry. Forinstance, some embodiments control 114 the distance between a patient'seyes and a display device 266, e.g., by having a test aide 264 place thepatient's chin on a rest or by instructing 120 the patient 256 to placetheir forehead against a rest, in a manner similar to that done whenusing a conventional refractor or conventional autorefractor. Someembodiments control 114 the lighting conditions, e.g., by giving 120 theoptometrist 264 or the patient 256 instructions for lowering ambientenvironment lights and/or for dilating the patient's pupils. Someembodiments use test patterns 214, at a variety of expected levels offocus and/or in different apparent or actual positions, in order toobtain 106 test results which can then be averaged 110, cross-referenced110 against one another, or otherwise used 110 to improve vision testaccuracy and/or reliability. Such testing condition controls 114 can beused to help provide 118 reproducible results and/or to calibrate thesystem 200 with the particular patient 256.

Some embodiments completely avoid 130 the use of physical lenses,including lens sets like those used in conventional refractors andconventional autorefractors. That is, the line of sight 262 from thedisplay 266 and its rendered digital image 214 to the eyes of the viewer256 does not go through any physical (i.e., glass, optical gradeplastic, fluid) lens, at least not as an intended part of the system 200design and operation. Other embodiments coordinate 132 the blurring 216and/or other refraction changes 108 made by the software 208 with thosemade by physical refraction lenses 254; the line of sight 260 in thesecases goes from the system display 266 through one or more physicallenses 254 to the viewer's eyes.

Accordingly, not every embodiment requires use of corrective lenses 254.That is, a system 200 may include, but does not always require, alens-based subjective refractor component and/or a lens-basedautorefractor component. It is contemplated that specific and usefulinformation may be obtained about the nature and extent of a person'srefractive errors, for example, without 130 any such use of correctivelenses. However, no prototype of the present invention has beenimplemented at this point, nor has any clinical testing of it been done.Accordingly, some embodiments of the present invention may becommercially or otherwise well suited for use in conjunction 132 withconventional vision testing tools and techniques that use correctivelenses 254. In particular and without excluding other uses, a givenembodiment may be used for initial tests, similar to the wayconventional autorefractors are often used, with the results 118 ofthose initial tests guiding the optometrist 264 in selecting lenses foruse in a conventional subjective refractor test.

To facilitate ease of use by optometrists 264, technicians 264, andothers who are familiar with the operation of conventional refractorsand conventional autorefractors, some embodiments provide 128 arefractor-style interface. This interface 240 may take the form ofconventional hardware (knobs, levers, etc.) interfaced with software 208via switches, pressure sensors, and the like. Alternately, some or allof the interface 240 may visually and operationally replicate 128 theconventional interface hardware on a screen 266, as a flight simulatorfor example replicates visually and operationally on a screen thehardware found in an airplane cockpit.

Not every embodiment need have a refractor-style interface. Forinstance, software embodiments may avoid or supplement the discrete lenscombinations of a refractor-style interface in order to provide muchsmoother changes 108 in image 214 refraction than is possible in aperceived image using movements of physical lenses. Accordingly, someembodiments depart from the discrete refraction changes inherent inconventional refractor interfaces, by providing continuous changes usinga slider bar, wheel rotation, or other interface 240 element forsmoothly controlled continuous change, or at least change that appearsto users as continuous. Instead of being asked to distinguish refractedimages as “better or worse” the viewer 256 may be asked 120 to stop whenthe image 268 is in focus. Moreover, the effective number of blurrings216 possible (and hence the number of different perceived images 268) ismuch larger in some embodiments than the number of lenses used in aconventional refractor or a conventional autorefractor, because changesare made to the source image 214 rather than being made merely byinterposing physical lenses.

Additional Examples

One system 200 includes a computing device having a display 266, a userinterface 240, a processor 202 operably connected with a memory 204, andsoftware 208 and user test data 208 configuring the memory andcontrolling the processor. In operation, this system displays 104 apattern 214 to a user 256; this is the “initial displayed pattern”. Theuser 256 sees 258 a resultant pattern, but due to refraction errorsand/or other flaws in the user's visual organs, the pattern 268 seen bythe user (the “initial perceived pattern”) is not precisely the same asthe initial displayed pattern 214. For instance, the initial perceivedpattern 268 may be blurred, spatially warped, or chromatically warped orshifted, may contain artifacts not displayed, or may otherwise differfrom the initial displayed pattern, depending on the nature of theproblems with the user's vision. Common refractive errors includespherical errors and cylindrical errors, but the present invention isnot limited to testing only for such errors.

The user 256 is then instructed 120 as to a target pattern. Theseinstructions may be written, spoken, or symbolic, for example. Forinstance, the user may be instructed 120 to “place all the dots in astraight line going from left to right across the middle of thedisplay”, or to “make each part of the picture equally blurry, using a‘blur-wand’ touched to the screen”. In response, the user interacts 106,260/262 with the system to change 108 the displayed image. This resultsin a “subsequent displayed pattern” 214 having changed pixel coordinates212, changed blurriness values 216, etc. in system memory, and thereforealso results in a new “subsequent perceived pattern” that is thesubsequent displayed pattern as seen by the user. For convenience, thevarious attributes of a pattern, such as source pixel data, cameraposition, lighting values and position, blurriness filters, and so on,may be conceptually grouped and treated as a single rendered digitalimage 210, but as noted these and other components may be organizeddifferently in different embodiments. By combining 110 the objectivechanges in pixel positions, blurriness, etc. in the system memory with atarget instruction template 208 representing the subjective change theuser 256 was instructed to seek (and also assuming good faith and somecompetence on the user's part), the vision testing system obtains 110information about the nature of the user's vision errors.

As a simple example, suppose that the initial displayed pattern includesseven dots equally spaced as shown in FIG. 3. The user 256 is instructed120 to “place the dots in a vertical line, equally spaced apart”. Theuser moves 106 the dots about, using a mouse, light pen, touch screen,or the like. The user produces the subsequent displayed pattern shown inFIG. 4, because the user sees 262 that pattern—through the user's ownvision system—as the subsequent perceived pattern shown in FIG. 5. Thatis, to the user it appears that the target pattern has been achieved. Inthis case, the target displayed pattern and the perceived pattern match,so FIG. 5 is also the template 208 for the target pattern. Thedifference between FIG. 4 and the target template in FIG. 5 indicates110 that the user 256 has a refractive error which maps the second dotfrom the top from the displayed position to the perceived position. Italso provides 118 a measure of that refractive error, for use inprescribing corrective lenses or corrective surgery.

As yet another example, consider a system 200 that has main componentsas in the example involving FIGS. 3 through 5, which operates byobtaining information about vision errors based on the differencebetween initial and subsequent displayed patterns and on the targettemplate. In this example, the system 200 presents an initial displayedpattern 214 that includes a grid of pixels represented in FIG. 6. Theuser 256 is instructed 120 to “make all parts of the image equallyblurry”. The user blurs 106 parts of the image using a light pen 206 asa blurring paintbrush 216 (e.g., as in the commercially available AdobePhotoShop program, although other blur filters 216 may be used toprovide a more rigorous and quantified correspondence 228 between blurresults and underlying refractive error causes). The user produces thesubsequent displayed pattern shown in FIG. 7, because the user sees 262that pattern—through the user's own vision system—as the subsequentperceived pattern shown in FIG. 8. FIG. 8 is also the template 208 forthe target pattern. The difference between FIG. 7 and the targettemplate in FIG. 8 indicates 110 that the user has a refractive errorwhich blurs the bottom two thirds of the leftmost column of pixels, andwhich partially blurs the rightmost column of pixels and the centerbottom row pixel, as indicated. That is, because the user sees FIG. 8 asthe perceived image 268 when given 104 FIG. 7 as an input, the softwarecan determine 110 that blurring not already done in FIG. 7 must becoming from the user's own vision system.

Conventional vision testing, especially for refraction errors, oftenstarts with a user view of some item, and then tries to improve theuser's view by changing the optical path, e.g., by inserting lensesbetween the user and the item to change refraction. Some embodiments ofthe present invention start with a user view, and then try to make partsof that view worse, e.g., by making the perceived view uniformly blurryby having the user blur parts of the view that are not perceived assufficiently blurry. Then the embodiment determines 110 refractiveerrors based on the target image and the user's changes—the areas theuser changed 106 less or not at all are those already blurred by theuser's own optics. That is, the embodiment asks the user 256 to changethe perceived quality 268 of the view, not necessarily to improve thatperceived quality.

CONCLUSION

Although particular embodiments of the present invention are expresslyillustrated and described herein as methods or systems, it will beappreciated that discussion of one type of embodiment also generallyextends to other embodiment types. For instance, the descriptions ofmethods in connection with FIG. 1 also help describe systems like thosedescribed in connection with FIG. 2, and vice versa. It does not followthat limitations from one embodiment are necessarily read into another.

The invention may be embodied in various ways, e.g., with processesand/or hardware on a server computer, on a client or peer, or on astandalone computer, software (data instructions) in RAM or permanentstorage for performing a method, general purpose computer hardwareconfigured by software, special-purpose computer hardware, listingreports or other data produced by a method, and so on.

Reference has been made to the figures throughout by reference numerals.Any apparent inconsistencies in the phrasing associated with a givenreference numeral, in the figures or in the text, should be understoodas simply broadening the scope of what is referenced by that numeral.

As used herein, terms such as “a” and “the” are inclusive of one or moreof the indicated item or step. In particular, in the claims a referenceto an item generally means at least one such item is present and areference to a step means at least one instance of the step isperformed.

Headings are for convenience only; information on a given topic may befound outside the section whose heading indicates that topic.

All claims as filed are part of the specification and thus help describethe invention, and repeated claim language may be inserted outside theclaims as needed.

While the present invention has been shown in the drawings and describedabove in connection with exemplary embodiments of the invention, it willbe apparent to those of ordinary skill in the art that numerousmodifications can be made without departing from the principles andconcepts of the invention as set forth in the claims. Although thesubject matter is described in language specific to structural featuresand/or methodological acts, it is to be understood that the subjectmatter defined in the appended claims is not necessarily limited to thespecific features or acts described above the claims. It is notnecessary for every means or aspect identified in a given definition orexample to be present or to be utilized in every embodiment of theinvention. Rather, the specific features and acts described aredisclosed as examples for consideration when implementing the claims.

The scope of the invention is indicated by the appended claims ratherthan by the foregoing description. All changes which come within themeaning and range of equivalency of the claims are to be embraced withintheir scope to the full extent permitted by law.

1. A method comprising: using vision-realistic rendering based onaberration data to produce a rendered digital image; presenting a personwith the rendered digital image; accepting, through a device, input fromthe person; changing the refractive sharpness of the rendered digitalimage in response to input accepted from the person; and calculatinginformation about the person's vision based at least on: input from theperson leading to a refractive sharpness change made during the changingstep, and a refraction model which relates visual acuity to changes inthe refractive sharpness of rendered digital imagery.
 2. The method ofclaim 1, further comprising a rendering step which uses vision-realisticrendering that employs at least one of the following: object space pointspread functions, an asymmetric ellipsoid model of vision, aspline-based model of vision, a wavelet-based model of vision.
 3. Themethod of claim 1, wherein the method provides the person with adisplay-blur-update loop.
 4. The method of claim 1, further comprising ablur challenging step which instructs the person to use an interfacetool to make specified portions of the rendered digital image equallyblurry.
 5. The method of claim 1, wherein the presenting step presentsthe rendered digital image in a software refractor interface, and theaccepting step accepts input from the person through the softwarerefractor interface.
 6. The method of claim 1, further comprisingobtaining a plurality of aberration sets which depend on input from theperson and on the refraction model.
 7. The method of claim 6, furthercomprising the step of estimating the person's accommodation toblurriness based on at least one of the aberration sets.
 8. The methodof claim 1, further comprising refracting the rendered digital imagethrough a physical lens before presenting the image to the person, andusing a refraction characteristic of the physical lens in calculatinginformation about the person's vision.
 9. A method comprising:producing, through vision-realistic rendering, a rendered digital image,wherein the producing step uses vision-realistic rendering based on atleast one of the following to produce the rendered digital image:hypothetical aberration data, gathered actual patient aberration data;presenting a person with the rendered digital image; accepting, througha device, input from the person; changing the refractive sharpness ofthe rendered digital image in response to input accepted from theperson; and calculating information about the person's vision based atleast on: input from the person leading to a refractive sharpness changemade during the changing step, and a refraction model which relatesvisual acuity to changes in the refractive sharpness of rendered digitalimagery.
 10. The method of claim 9, wherein the changing step changesthe refractive sharpness of only part of the rendered digital image. 11.The method of claim 9, wherein the method provides the person withinteractive reverse vision-realistic rendering.
 12. The method of claim9, wherein the calculating step calculates a vision correctionrecommendation, and the method further comprises reporting the visioncorrection recommendation.
 13. The method of claim 9, further comprisingrefracting the rendered digital image through a physical lens beforepresenting the image to the person, and using a refractioncharacteristic of the physical lens in calculating information about theperson's vision.
 14. A system, comprising: a processor in operableconnection with a memory; the processor configured by data andinstructions to perform the following: produce, through vision-realisticrendering, a rendered digital image; present a person with the rendereddigital image; accept, through a device, input from the person; changethe refractive sharpness of the rendered digital image in response toinput accepted from the person; obtain a plurality of aberration setswhich depend on input from the person and on a refraction model whichrelates visual acuity to changes in the refractive sharpness of rendereddigital imagery; estimate the person's accommodation to blurriness basedon at least one of the aberration sets; and calculate information aboutthe person's vision based at least on: input from the person leading toa refractive sharpness change made during the changing step, and therefraction model.
 15. The system of claim 14, wherein the aberrationsets comprise a sequence of hypothetical aberration data sets used tocalculate information about the person's vision.
 16. The system of claim14, wherein the system provides the person with interactive control ofblurriness in presented rendered digital imagery.
 17. The system ofclaim 14, wherein the system accepts input through a software refractorinterface.
 18. The system of claim 14, wherein the system is free ofphysical lenses interposed between the rendered digital imagery and theperson's eyes.
 19. The system of claim 14, further comprising a physicallens which refracts the rendered digital image, and wherein a refractioncharacteristic of the physical lens is used in calculating informationabout the person's vision.
 20. The system of claim 14, furthercomprising a means for measuring the person's accommodation toblurriness.